(1). The first approximation of restes of weathering and soil fromation : A new method for evaluation of raytes of weathering and soil formation was proposed. For the elements derived from rocks, geochemical mass balances were assumed to exist between parent rocks, soils, and river waters. Seven mass balance equations, which include the rates of weathering (denoted as R) and soil formation (denoted as S) in unknown quantitites, were set up using the data of Al, Fe, Ca, K,Na, and Si. Solution of simultaneous equations gave vakues of R and S.(2). The multiple regression method for estimating rates of weathering and soil formation : Distribution of the seven maojer elements among rocks, soils, river water precipitation and vegetation were formulated in seven mass balance equations. Multiple regression analysis gave one set of the most probable values of rates of weathering and soil formation in a watershed.(3). Characterization of precipitation and river water chemistry for measuring rates of weathering and soil formation in small watersheds : The precipitation and river water chemistry were characterized in three small subwatersheds of the Iu river, southwestern Japan. The monitoring of the precipitation and river water was continued during April 1989-March 1992. The three subwatersheds consist of different geological materials : andesite, granite, and basic pyroclastic materials.(4). Rock and soil chemistry in small watersheds : Characterization of rocks and soils from andesitic and garnitic subwatersheds was done. Heterogenity of soil due to topografic positions was observed. Sampling strategy for rocks and soils were proposed.(5). Characterization of tropical watershed of Wes Sumatra : For case study, long term monitoring was continued during September 1991 to December 1992 at andesitic small watershed in G.Gadut catchment area, West Sumatra, Indonesia.